Force summing multiplex actuator

ABSTRACT

Four rotary-to-linear motion transducers each responsive to a separate but equal control signal are coupled together in a force summing arrangement to produce a linear motion output. Each of the rotary-to-linear motion transducers is part of a control channel that includes an asymmetrical breakaway force coupler for transmitting the linear motion output of the transducer to an attachment point on a torque tube. The breakaway coupler has a force responsive disconnect that is actuated when the force developed between the attachment point and the rotary-to-linear motion transducer exceeds a preset level. When the force between the attachment point and the transducer output exceeds the preset level, the disconnect actuates a switch to isolate the transducer for that channel from the control signal. Also included in each of the control channels is a position transducer for generating a feedback signal to balance out the generated control signals. At the output of the torque tube a linkage arrangement converts the rotary torque tube motion into a linear displacement that varies in accordance with the control signals.

llnited States Patent [151 354mm Koch et al. Feb. 8, 1972 [54] FURCESUMMING MULTIPLEX Primary ExaminerEdgar W. Geoghegan ACTUATOR AssistantExaminer-Clemens Schimikowski AttameyRichards, Harris & Hubbard andJames D. Will- [72] Inventors: Werner G. Koch, Arlington; Jack McCurbornley, Dallas, both of Tex.

73 Assignee: LTV Electrosystems, Inc., Dallas, Tex. [571 ABSTRACT [22]Filed: Feb 2, 1970 Four rotary-to-linear motion transducers eachresponsive to a separate but equal control signal are coupled togetherin a 1 PP 7,673 force summing arrangement to produce a linear motionoutput. Each of the rotary-to-linear motion transducers is part of [52]U S Cl 91/] 91/361 74/424 8 a control channel that includes anasymmetrical breakaway 267/1319 91 I force coupler for transmitting thelinear motion output of the [5'] in CI Fmb 25/26 FOIbBI/IZ transducer toan attachment point on a torque tube. The 58' Fie'ld 459 {67/170 174breakaway coupler has a force responsive disconnect-that is 2 7 74/124actuated when the force developed between the attachment point and therotary-to-linear motion transducer exceeds a preset level. When theforce between the attachment point [56] References Cited and thetransducer output exceeds the preset level, the discon- UNITED STATES PAS nect actuates a switch to isolate the transducer for that channel fromthe control signal. Also included in each of the con- 3,198,082 8/1965Kems ..9l/l 1 channels is a position transducer generau'ng a f d-1464519 9/1969 Sherman back signal to balance out the generated controlsignals. At 3,095,783 7/1963 Flmdt the output of the torque tube alinkage arrangement converts 21801 ,617 8/1957 LeLan the rotary torquetube motion into a linear displacement that 1 g l ----t---- varies inaccordance with the control signals. ep an e Claims, 6 Drawing Figures l74 76 72 /3 C r T l 1 A sw SW E M E M f a CONVERTER CONVERTER To K 66 K68 WCOMPARE E M H E |V| CONVERI ER CONVERTER 7/ l l 73 5 SW f sw o F L/a 3 A [2 75 f 77 58 80 l l6 '-+:i+:i+-- l l 6| L J SHEET 1 OF 3INVENTORS; WERNER G. KOCH E/M CONVERTER MULTIPLEX ACTUATOR PILOT JACKMCURLEY ATTORNEYS PNWTEB FEW 8 sum 3 0r 3 FIG 4 .n lENTORS: WERNER G.KOCH JACK MCURLE Y ATTORNEYS FORCE SUMMING MULTIPLEX ACTUATOR Thisinvention relates to a multiplex actuator, and more particularly to aforce summing redundant channel multiplex actuator.

It was early realized that as aircraft increase in size and speed thatconventional cable and mechanical linkage control mechanisms areinadequate and there is a need for electrical flight control systems.There has, however, been some reluctance to accept the electrical flightcontrol system because it is thought that mechanical systems are morereliable. To improve the reliability of electrical control, a system ofredundant parallel channels has been implemented.

Heretofore, approaches for providing redundancy have typically resultedin double control chains or channels in which a failure in one channelhopefully would permit the other channels to carry on the necessarycommand functions. Such a system, depending upon the particular failuresuffered, generally experienced at least degradation of control when thefailed channel must be dragged" by the operating channel or channels. I

When redundant control channels are employed to improve the systemreliability the several channels must eventually terminate at a singlemaster power drive that positions the control surface of the aircraft.The several channels may be brought together at the master power driveeither in a force summing" configuration or a displacement summing"configuration.

When the several channels of a redundant controlsystem are displacementsummed, the output of each channel is combined in a series arrangement.Displacement summing (series summing) has the advantage that theremaining active channels do not have to drag the failed channel. In theconventional displacement summing system, the several redundant channelsare combined to produce the total desired range of movement for theaircraft control surface. Upon a failure of one of these channels, someloss of stroke of the master power drive results with the attendant lossin the range of movement of the control surface.

In the forcing summing configuration, the outputs of the severalchannels are connected to a common summing point. The forces developedby each of the channels are summed at this common point into a singleforce motion. Upon a failure of any one of the several channels, theremaining channels will continue to positionthe aircraft controlsurfaces through the full range of operation. Heretofore, in the forcesumming arrangements, the failed channel created a drag on the remainingactive channels. Another of the disadvantages of previous force summingsystems is that a jam" in any one of the several channels may result ina catastrophic failure.

An object of this invention is to provide a multiplex actuator in aredundant control system wherein the actuator has full stroke outputcapabilities upon a failure of all but two of the redundant channels.Another object of this invention is to provide a multiplex actuator in aredundant control system wherein the several control channels are forcesummed. A further object of this invention is to provide a multiplexactuator in a redundant control system wherein the failure of one of theseveral channels does not produce a drag on the remaining activechannels. Still another object of this invention is .to provide amultiplex actuator in a redundant control system wherein malfunctioningchannels are disconnected from the control signals.

In accordance with this invention, a multiplex actuator having an outputmotion that varies in accordance with generated control signals includesa plurality of control channels with each channel havingrotary-to-linear motion transducer responsive to a separate one of thegenerated control signals. The linear motion output of the transducerfor each channel is transmitted to an attachment point when a forceapplied to a breakaway force coupler is below a breakout value. If theforce between the attachment point and the output of the motiontransducer exceed the breakout value by a given amount, a switch carriedby the coupler is actuated, thereby disconnecting the transducer fromthe generated control signal.

Each of the several control channels connects to a force bar at theattachment point to produce an output motion that varies in accordancewith the generated signal energizing each of the control channels.

In accordance with a more specific embodiment of the invention, amultiplex actuator for positioning an aircraft control surface by meansof a power ram in accordance with pilot generated control signalsincludes a first control channel pair coupled together in a forcesumming arrangement to a common attachment point. Each of the controlchannels includes: a rotary-to-linear motion transducer responsive to aseparate one of the pilot generated control signals; a breakaway forcecoupler engaging the output of the transducer for transferring thelinear motion thereof to the common attachment point when the forceapplied between the attachment point and the transducer is below abreakout value; and a switch carried by the coupler and actuated whenthe force applied thereto exceeds by a given amount the breakout valueto disconnect the transducer from the generated control signal. A:second control channel pair is also force summed at a common attachmentpoint. Each of the control channels of the second pair is similar tothose of the first pair. The common attachment points of the two.control channel pairs are connected to a torque tube that produces anoutput motion in accordance with the pilot generated signals to thevarious control channels. A rotary-to-linear motion transducer convertsthe rotary output of the torque tube into a linear motion forcontrolling the power ram.

A more complete understanding of the invention and its advantages willbe apparent from the specification and claims and from the accompanyingdrawings illustrative of the invention.

Referring to the drawings:

FIG. 1 is a schematic ofa redundant controlsystem including a forcesumming multiplex actuator having a linear output coupled to aservo-valve for controlling a power ram connected to an aircraft controlsurface;

FIG. 2 is a block diagram of a quadruplex input force summing actuatorproducing a linear output for coupling to a servo-valve; I

FIG. 3 is a schematic of a quadruplex input force summing actuatoremploying rotary-to-linear motion transducers and breakaway forcecouplers;

FIG. 4 is a cross section of the transducer and breakaway force couplerof one channel of the actuator of FIG. 3;

FIG. 5 is a plot of force as a function of displacement for a breakawayforce coupler of the system of FIG. 3; and

FIG. 6 is a cross section of a breakaway force coupler havingcomplimentary release characteristics from the coupler of FIG. 4.

Referring to FIG. 1, there is shown a multiplex actuator 10 having fourelectrical signals applied to terminals 11 through 14. These controlsignals may be generated in a conventional manner by a stick transducerthat converts a mechanical input from a pilots control stick intoelectrical signals. The pilot's control input, converted into electricalsignals by the stick transducer, is transmitted to the terminals 11through 14 by a parallel arrangement of wires which may be located atdifferent paths in the air frame to minimize the possibility of adisruption of all the pilot generated control signals to the actuator10. In addition to pilot generated signals the electrical signals onterminals 11 through 14 may be received from autopilot sensors, astability augmentation system, or from other systems, such as anavigation control.

The multiplex actuator 10 produces a linear motion output on aconnecting rod 16; the linear motion varies in accordance with the pilotgenerated control signals on the terminals 11 through 14 in a manner tobe described. Coupled to the output of the actuator 10 is a dual tandemservo-valve 18 providing fluid pressure signals to a dual tandem powerram 20. The servo-valve 18 includes a cylinder 22 having a spool valve24 slidably disposed therein and including interconnected lands 25through 31. Conduits 32 and 34 interconnect the first section of theservo-valve 18 to a pressure supply and reservoir (neither shown),respectively. Similarly, conduits 36 and 38 connect the second sectionof the valve 18 to a source of fluid pressure and a fluid reservoir(neither shown), respectively. Conduits 40 and 42 interconnect the firstsection of the valve 18 to the first stage of the power ram 20 onopposite sides ofa piston 48. Conduits 44 and 46 similarly interconnectthe second stage of the valve 18 to the second stage of the power ram 20on opposite sides ofa piston 50.

Pistons 48 and 50 of the power ram 20 are interconnected on a piston rod52 that has an external coupling to a link 54. Link 54 is intended torepresent the mechanical linkage between a power ram and one of thecontrol surfaces 56 of an aircraft. The piston rod 52 is in the form ofahollow shaft and is positionable over a linear voltage differentialtransformer 58 that generates four separate but equal position feedbacksignals on lines 59 through 62. Feedback signals on the line 59 through62 are applied to the multiplex actuator to balance the pilot generatedsignals on the terminals 11 through 14 to stop the motion of theconnecting rod 16 at a new desired position.

Referring to FIG. 2, there is shown a quadruplex force summing actuatorwherein the pilot generated signals are applied to the terminals 11through 14. At present, quadruplex actuators provide the most favorabledegree of redundancy for many actuator applications, but any degree ofredundancy may be used with the force summing system of the presentinvention.

The system of FIG. 2 consists of four control channels and includeselectromechanical converters 66 through 69, summing amplifiers 70through 73 responsive to the pilot control signals and feedback signals,and disconnect switches 74 through 77. Output connecting rods of theconverters 66 through 69 are coupled to a torque tube 78 which sums theconverter outputs into an oscillating motion. This oscillating motion isthen converted into a linear displacement for driving the dual tandemservo-valve 18 through the connecting rod 16. The four-channel linearvoltage differential transformer (LVDT) 58 is illustrated responsive tomovement of the servovalve 18 through a linkage 80 that is intended torepresent the operation of the power ram in response to signals from theservo-valve 18. The four-unit LVD transformer 58 is used to provideelectrical signals which are proportional to the position of the controlsurface 56 for the system followup or feedback loop. Typically, afour-unit LVDT is a cluster of four separate transducers in a commonhousing.

Referring to FIG. 3, there is shown the four electromechanicalconverters 66 through 69 coupled to the torque tube 78. Converters 66and 68 are coupled together in a force summing arrangement at a commonattachment point 82 connected to the tube 78. Similarly, converters 67and 69 are coupled in a force summing arrangement at a common attachmentpoint 84, also connected to the tube 78.

Converter 66 includes a rotary-to-linear motion transducer 86 having anoutput shaft 88 engaging a breakaway coupler 90. The breakaway coupler90 transmits the motion of the output shaft 88 to the attachment point82 as a rigid link when the force developed across the coupler is belowan established breakout level. In a similar arrangement, the converter67 comprises a rotary-to-linear motion transducer 92 having an outputshaft 94 engaging a breakaway coupler 96. Coupler 96 transmits motion atthe output shaft 94 to the common attachment point 84. The converter 68includes a rotary-tolinear motion transducer 98 having an output shaft100 engaging a breakaway coupler 102 that connects to the attachmentpoint 82. The fourth channel ofthe system illustrated includes theconverter 69 which comprises a rotary-to-linear motion transducer 104having an output shaft 106 engaging a breakaway coupler 108. Coupler 108transmits the motion of the output shaft 106 to the attachment point 84when the force developed across the coupler is below the breakout level.

Rotary oscillating motion produced on the torque tube 78 by forcesumming the output motion of the rotary-to-linear transducers of theconverters 66 through 69 is converted into a linear displacement forpositioning the servo-valve 18 through a mechanical linkage. Themechanical linkage includes an arm 110 attached to the torque tube 78and having a pivotal connection to a connecting link 112. Link 112 alsohas a pivotal connection to an arm 114 secured to a stub shaft 116. Thestub shaft 116 includes a sliding member 118 engaging the spool valve 24of the servo-valve 18. It should be understood, that the illustration ofa torque tube 78 and the mechanical linkage arrangement connected to theservo-valve 18 is intended as showing only one embodiment of forcesumming mechanism for the four control channels.

Referring to FIG. 4, there is shown in cross section theelectromeehanical converter 66 for the control channel of the actuatorsystem of FIG. 2. The other converters of the actuator are similarlyconstructed. The rotary-to-linear motion transducer 86 has a permanentmagnet stator 120 mounted in a housing 122. The pilot generated signalis applied through a connector 124 to a brush ring 165 and then to anarmature 126. The armature 126 rotates, by the interaction between itselectrical field and the magnetic field of the stator 120. It is mountedto rotate in the housing 122 by means of bearings 128 and 130. A ballnut 131 is fixed to the armature 126 and engages a lead screw 132 thatextends through the housing 122 as part of the output shaft 88. Linearmotion results from the operation of the lead screw 132 and the ball nut131. This ball-screw arrangement provides a high-efficiency gearing andallows the individual converters to be back driven in the event of afailure. To produce this linear motion, the lead screw 132 is restrainedfrom rotating by means ofa dowel pin 134.

Also included as part of the transducer 86 is a linear voltagedifferential transformer 136 threaded into the housing 122 and engagingthe lead screw 132 for generating a position feedback signal. Thisfeedback signal is transmitted through the connector 124 to the summingamplifier 70, as explained. The transducer position feedback signal plusthe feedback signal from the power ram are thus both summed in theamplifier 70 to balance the pilot generated control signal at terminal11.

An output motion from the transducer as evidenced by movement of thelead screw 132 is transmitted to the attachment point 82 through thebreakaway force coupler 90. As illustrated in FIG. 4, the breakawaycoupler includes a connecting rod 138 coupled to the output shaft 88 ofthe rotaryto-linear motion transducer. A detent 140 at the extreme endof the rod 138 is provided to control the actuation of a microswitch142. During the normal operation of the converter 66, a roller 144 atthe end of an actuating arm 146 for the switch 142 fits into the detent140. When the rod 138 moves either to the left or right of the positionshown, the roller 144 engages the rod thereby actuating the switch 142.Switch 142 has lead wires (not shown) connected to the disconnect 74.When the switch 142 is actuated, it energizes the disconnect 74 toisolate the rotary-to-linear motion transducer 86 from the amplifier 70.By properly sizing the detent 140, some movement of the rod 138 mayoccur without actuating the switch 142.

In normal operation, the rod 138 is held in a fixed position therebyforming a rigid coupling between the output shaft of the transducer 86and the attachment point of the breakaway coupler 90. To maintain therod 138 in a fixed position relative to the housing 148 of the coupler90, two springs 150 and 152 are preloaded into the housing betweencollets 154, 156 and 158. In the position shown, the collet 154 engagesa shoulder on the rod 138 and one end of the housing 148. The collet 156is restrained on the rod 138 by means ofa retaining ring 160. The spring152 is preloaded between the collets 154 and 156. Collet 158 is movablewith respect to the collet 156 and the housing 148; in the positionshown, it is at rest against the housing 148 and a shoulder of thecollet 156. The spring 150 is preloaded between the col et 154 and thecollet 158.

An important feature of the actuator of the present invention is theasymmetrical breakout of the coupler 90. That is, the force required tomove the rod 138 with respect to the housing 148 in one direction isdifferent than the force required to move the rod in the oppositedirection. Consider that the output shaft of the transducer 86 is heldstationary and the housing 148 has a force exerted thereon tending tomove it toward the'left. The force required to move the rod 138 relativeto the housing 148 in this case must be sufficient to overcome thepreload of the springs 150 and 152. A force tending to move the housing148 toward the left will cause the collet 154 to follow the housing andbecome disengaged from the shoulder on the rod 138. The collets 156 and158, however, will remain in the position illustrated relative to therod 138 by means of the retaining ring 160. Thus, the preload of bothsprings must be overcome to displace the rod 138 relative to the housing148. Now if it is assumed that a force is exerted on the housing 148tending to move it toward the right, then collect 158 will move towardthe right with respect to the collect 156. The collets 154 and 156,however, will be held in the spaced relationship shown by means oftheshoulder on the rod 138 and the retaining ring 160, respectively. Thus,to displace the housing 148 toward the right with respect to the rod138, requires only a force sufficient to overcome the preload of thespring 150. In this case, the spring 152 is bypassed. Accordingly, thebreakout of the coupler 90 is asymmetrical between the extend andretract displacement of the transducer 86.

Referring to FIG. 5, there is shown a plat of force versus dis placementfor the extend and retracted directions. Before displacement takes placebetween the rod 138 and the housing 148 in the extend direction, thatis, movement of the lead screw 132 toward the left, a force must bedeveloped as indicated by the intersection of the vertical axis and theline 162. After the initial breakaway force has been exceeded,additional displacement between the rod 138 and the housing 148 takesplace as the force increases as along the line 162. In the retractdirection, that is, movement of the lead screw 132 toward the right, adisplacement between the rod 138 and the housing 148 will take placewhen a force is developed that exceeds that indicated by theintersection of the line 164 and the vertical axis. Again, additionaldisplacement will be developed as the force increases as along the line164.

By providing asymmetrical breakout in the coupler 90, a positivepositioning of the torque tube 78 is assured. Because of manufacturingtolerances, the displacement developed by two converters, such asconverters 66 and 68, will not be equal even though both converters arecontrolled from identical signals. One or the other of the twoconverters will produce a greater displacement than the other for thesame control signal. When this occurs, one of the couplers 90 willbreakaway thereby displacing the rod 138 from the housing 148. Theremaining coupler, however, will remain rigid thereby fixing theposition of the torque tube 78,

To couple two converters to a common attachment point in an opposingforce summing configuration the breakout ofthe two opposing couplersmust be in the same direction. That is, between the couplers 90 and 102,if the extend breakout of the coupler 90 is less than the retractbreakout, than for the coupler 102 to retract breakout must be less thanthe extended breakout.

Referring to FIG. 6, there is shown a cross section of the coupler 102providing asymmetrical breakout in the reverse direction from thecoupler 90. The same reference numerals will be used to show thesimilarity and differences between the couplers 90 and 102. Connectingrod 138 of the coupler 102 is maintained in a fixed spaced relationshipwith respect to the housing 148 by means of the preloaded springs 150and 152. Collets 154, 156 and 158 maintain the springs 150 and 152 inthe preloaded condition. Collet 154 is positioned on the rod 138 againstthe retaining ring 160 and engages the housing 148. Collets 156 and 158are shown positioned against the shoulder of the rod 138 and the housing148, respectively.

Assume the output shaft of the transducer 98 is held in a fixedposition, then to displace the rod 138 of the coupler 102 with respectto the housing 148 a force must be exerted on the coupler housing towardthe right which is sufficient to overcome the preload of both springsand 152. With the collet arrangement as illustrated in FIG. 6, movementof the housing 148 toward the right carries with it the collet 154 whichthen moves away from the retaining ring 160. Both springs 150 and 152must thus becompressed before a displacement between the rod 138 and thehousing 148 takes place. A force exerted on the housing 148 of thecoupler 102 toward the left which is sufficient to overcome the preloadof the spring 150 causes the collet 158 to move with respect to thecollet 156. The spring 152 in this case moves with the rod 138 and thusdoes not effect the total force required to cause a displacement betweenthe coupler rod and coupler housing. This operation is the reverse ofthat described previously with respect to the coupler 90 of FIG. 4.

By arranging the couplers 90 and 102 as illustrated, the breakaway forcewill always be greater in one direction (toward the right) than theother (toward the left). A. similar arrangement is provided between thecouplers 96 and 108. Coupler 96 being similar to coupler 90 and coupler108 being similar to coupler 102.

In operation, a pilot generated signal at the terminal 11 appears as anoutput voltage from the summing amplifier 70 to drive theelectromechanical converter 66 through the disconnect 74. The outputshaft of the converter 66 either extends or retracts depending on themagnitude and polarity of the pilot generated signal. A'positionfeedback signal from a feedback transducer in the converter 66 isapplied to one input of the summing amplifier 70 to balance the pilotgenerated signal. A separate but equal pilot generated signal at theterminal 13 is processed through the summing amplifier 72 to drive theelectromechanical converter 68 through the disconnect 76. By properlypolarizing the signals to the converters 66 and 68, the same pilotcontrol signals will cause one of the converters to extend the outputshaft while the other retracts thus producing a combined movement in onedirection at the attachment point 82. If the displacement of the outputshaft of the converters 66 and 68 are exactly equal, the breakawaycoupler in each of these units will remain a rigid link between theattachment point 82 and the respective rotary-to-linear motiontransducer. If, however, the output of one of the converters isdisplaced more than the other, one of the breakaway couplers willbreakout, thereby disconnecting the respective transducer from a rigidlink to the attachment point. Note that so long as this breakoutmovement is such that the switch 142 is not actuated, the transducer ofthe affected channel will be coupled to the summing amplifier output.

A similar control channel pair is attached to the attachment point 84. Apilot generated signal at the input terminal 12 appears at the outputterminal of the summing amplifier 71 to drive the electromechanicalconverter 67 through the disconnect 75. A feedback signal from theposition transducer of the converter 67 appears at a second input to theamplifier 71 to balance out the pilot generated signal. The fourth pilotgenerated signal appearing at the input terminal 14 is applied to thesumming amplifier 73 that generates an output for driving theelectromechanical converter 69 through the disconnect 77. Converter 69also includes a position transducer for generating a feedback signalconnected to a second input of the summing amplifier 73 to balance outthe pilot generated signal. Converters 67 and 69 are coupled to theattachment point 84 in a force summing arrangement. These two convertersare polarized in a manner such that when the output shaft of one isextending, the output shaft of the opposite is retracting tovproduce anet movement in one direction at the attachment point 84. I

As oscillating motion imparted to the torque tube 78 by operation of theconverters 66 through 69 is converted into a linear displacement of theconnecting rod 16 to position the servo-valve 18. The power ram 20responds to signals generated by the servo-valve l8 and moves thecontrol surface 56 in accordance with the pilot generated signals. Thelinear voltage differential transformer 58 of the power ram generatesfour position feedback signals each coupled to one of the summingamplifiers 70 through 7.3. These position feedback signals are a finaladjustment to balance out the pilot generated signals and produce thedesired output from the converters 66 through 69.

Should a malfunction occur such that the converter unit of one channelno longer provides the correct force to the torque tube 78, thebreakaway coupler of that channel will break out. When the breakoutdisplacement of the coupler exceeds a given amount, the disconnect inthat channel will be actuated by the coupler carried switch, therebyisolating the converter from the pilot generated signal. With the signalto a converter cut off through the disconnect, the breakaway coupler ofthat converter will return to a nonbreakout state. In such a situation,the converter will be back driven by the remaining active channels withlittle, if any, performance degradation. Such operation is possiblebecause of the highly efficient ball-screw unit. The active channels areable to back drive the failed channel and still provide a nearly normaloutput performance.

After one channel has failed due to a malfunction, it can be reactivatedby the pilot through a reset circuit in the disconnect. Such a featureis desirable since the original malfunction may be temporary andself-correct after a short time. By providing a reset in the disconnect,the system can be checked out. A simulated failure is injected into eachchannel in sequence. After the check out the channels are reactivatedthrough the reset circuit.

If a failure in one channel is the result ofajam in the armature ormotor, the breakaway coupler enables the remaining unit to continue toprovide a control function. When ajam occurs in a converter, thebreakaway coupler in that channel continues to break out as theremaining active channels continue to position the torque tube 78.

Each of the channels of the actuator is also continuously monitored by acomparator circuit 168 that determines the number of channels that havemalfunctioned. When any two of the four channels malfunction, leavingonly two remaining active channels, the comparator circuit 168 willgenerate an alarm signal to the pilot. With only two active channels,there is the possibility that if one of the remaining channelsmalfunctions it will overpower the other active channel. This may causethe control surface 56 to be positioned hard-over resulting in acatastrophic failure. When the pilot is signaled that only two of thefour channels are still active, he may make proper corrective action tominimize the possibility ofa hardover positioning ofthe control surface.

While only one embodiment of the invention, together with modificationsthereof, has been described in detail herein and shown in theaccompanying drawings, it will be evident that various furthermodifications are possible with departing from the scope of theinvention.

What is claimed is:

l. A multiple actuator having an output motion that varies in accordancewith generated control signals, comprising:

a plurality of control channels each including a rotary-tolinear motiontransducer response to a separate one of the generated control signals,motion transmitting means for transferring the linear motion produced bythe transducer to an attachment point, said motion transmitting meanshaving:

a. first and second members movable relative to each other, one membercoupled to the output of the transducer and the second member coupled tothe attachment point,

b. first means for restraining the movement of the first and secondmembers relative to each other in a first direction below a firstbreakout value, and

c. second means for restraining the movement of the first and secondmembers relative to each other in a second direction below a secondbreakout value greater than the first breakout value,

and switching means carried by said motion transmitting means andactuated thereby when the force applied thereto exceeds the breakoutvalues to disconnect the transducer from the generated control signal,and a forcing bar having the attachment point of each of the pluralityof control channels connected thereto and producing an output motionvarying in accordance with the generated signal energizing each of thecontrol channels. 2. A multiplex actuator having an output motion thatvaries 10 in accordance with generated control signals, comprising:

a plurality of control channels each including a rotary-tolinear motiontransducer responsive to a separate one of the generated controlsignals, and motion transmitting means coupled to the output of thetransducer for transferring the linear motion produced thereby to anattachment point, said motion transmitting means including:

a. first and second members movable relative to each other, one membercoupled to the output of the transducer and the second member coupled tothe attachment point,

b. first means for restraining the movement of the first and secondmembers relative to each other in a first direction below a firstbreakout value, and

c. second means for restraining the movement of the first and secondmembers relative to each other in a second direction below a secondbreakout value greater than the first breakout value, and

a force bar having the attachment point of each of the plurality ofcontrol channels connected thereto and producing an output motionvarying in accordance with the generated signals energizing each of thecontrol channels.

3. A multiplex actuator having an output motion that varies inaccordance with generated control signals as set forth in claim 2including a position transducer in each of the control channels coupledto said rotary-to-linear motion transducer for generating a positionfeedback signal from the motion transducer to balance out the generatedcontrol signal applied thereto.

4. A multiplex actuator having an output motion that varies inaccordance with generated control signals as set forth in claim 2wherein said force bar is a torque tube having a pivotal connection toeach of said plurality of control channels and producing a rotary outputfrom said actuator.

5. A multiplex actuator having an output motion that varies inaccordance with generated control signals, comprising:

a plurality of control channels each including a rotary-tolinear motiontransducer responsive to a separate one of the generated controlsignals, and motion transmitting means coupled to the output of thetransducer for transferring the linear motion produced thereby to anattachment point, said motion transmitting means including:

a. a housing pivotally connected to the attachment point,

b. a connecting rod slidably positioned in said housing and coupled tothe output of said motion transducer,

c. a first collet fitted over said rod and engaging a stop thereon andsaid housing, a second collet also fitted over said rod and engaging astop thereon,

e. a first spring positioned between said first and second collets in apreloaded condition,

f. a third collet concentrically mounted with said second collet andmovable with respect thereto and engaging said housing, and

g. a second spring positioned between said first and third collets in apreloaded condition, said first and second springs establishing anasymmetrical breakout force for movement of the connecting rod withrespect to the housing, and

a force bar having the attachment point of each of the plurality ofcontrol channels connected thereto and producing an output motionvarying in accordance with the generated signals energizing each of thecontrol channels.

6. A multiplex actuator for positioning an aircraft control surface inaccordance with pilot generated control signals, comprising:

a plurality of control channels each including a rotary-tolinear motiontransducer responsive to a separate one of the generated controlsignals, a breakaway force coupler coupled to the output of thetransducer for transferring the output motion to an attachment point,said breakaway force coupler including:

a. first and second members movable relative to each other, one membercoupled to the output of the transducer and the second member coupled tothe attachment point,

b. first means for restraining the movement of the first and secondmembers relative to each other in a first direction below a firstbreakout value, and

c. second means for restraining the'movement of the first and secondmembers relative to each other in a second direction below a secondbreakout value greater than the first breakout value, and

switching means carried by the breakaway coupler and actuated therebywhen the force applied thereto exceeds by a given amount the breakoutvalues to disconnect the transducer from the generated control signal,

a position transducer in each of the control channels coupled to said.rotary-to-linear motion transducer for generating a position feedbacksignal connected to the respective amplifier for that channel, and

a force bar having the attachment point of each of the plurality ofcontrol channels connected thereto and producing an output motion forcontrolling a power ram connected to said aircraft surface for varyingthe position of said surface in accordance with the pilot generatedcontrol signals.

7. A multiplex actuator for positioning an aircraft control surface asset forth in claim 6 including means for monitoring the output of all ofsaid plurality of control channels and generating an alarm signal whenthe switching means carried by all but two of said channels is actuated.

8. A multiplex actuator for positioning an aircraft control surface asset forth in claim 6 wherein said force bar is a torque tube having apivotal connection to each of said plurality of control channels andproducing a rotary output, and including a rotary-to-linear motiontransducer for generating the control signals to said power ram.

9, A multiplex actuator for positioning an aircraft control surface asset forth in claim 6 wherein said rotary-to-linear motion transducerincludes a lead screw connected to said breakaway coupler and a ball-nutassembly as part of a motor armature, said lead screw and ball-nutassembly may be back driven by a force applied to the output of saidtransducer.

10. A multiplex actuator for positioning an aircraft control surface inaccordance with ilot generated control signals, comprising:

a plurality of control channels each including a rotarytolinear motiontransducer responsive to a separate one of the generated controlsignals, a breakaway force coupler coupled to the output of thetransducer for transferring the output motion to an attachment point,said breakaway force coupler including:

a. a housing pivotally connected to the attachment point,

b. a connecting rod slidably positioned in said-housing and coupled tothe output of said motion transducer,

c. a first collet fitted over said rod and engaging a stop thereon andsaid housing,

d. a second collet also fitted over said rod and engaging a stopthereon,

e. a first spring positioned between said first and second collets in apreloaded condition,

f. a third collet concentrically mounted with said second collet andmovable with respect thereto andengaging said housing, and

g. a second spring positioned between said first and third collets in apreloaded condition, said first and second springs establishing anasymmetrical breakout force for movement of the connecting rod withrespect to the housing, and

switching means carried by the breakaway coupler and actuated therebywhen the force applied thereto exceeds by a given amount the breakoutvalues to disconnect the transducer from the generated signal,

a position transducer in each of the control channels coupled to saidrotary-to-linear motion transducer for generating a position feedbacksignal connected to the respective amplifier for that channel, and

a force bar having the attachment point of each of the plurality ofcontrol channels connected thereto and producing an output motion forcontrolling a power ram connected to said aircraft surface for varyingthe position of said surface in accordance with the pilot generatedcontrol signals.

11. A multiplex actuator for positioning an aircraft control surface bymeans of a power ram in accordance with pilot generated control signals,comprising:

a first control. channel pair coupled together in a force summingarrangement to a common attachment point, each of said control channelsincluding a rotary-to-linear motion transducer responsive to a separateone of the generated control signals, a breakaway force coupler engagingthe output of the transducer for transferring the linear motion outputthereof to the common attachment point, said breakaway force couplerincluding:

a. first and second members movable relative to each other, one membercoupled to the output of the transducer and the second member coupled tothe attachment point,

b. first means for restraining the movement of the first and secondmembers relative to each other in a first direction below a firstbreakout value, and

c. second means for restraining the movement of the first and secondmembers relative to each other in a second direction below a secondbreakout value greater than the first breakout value, and

switching means carried by the coupler and actuated thereby when theforce applied thereto exceeds by a given amount the established breakoutvalues to disconnect the transducer from the generated control signal,

a second control channel pair coupled together in a force summingarrangement to a common attachment point, each of the control channelsincluding a rotary-to-linear motion transducer responsive to a separateone of the generated control signals, a breakaway force coupler engagingthe output of the transducer for transferring the linear motion outputthereof to the common attachment point, said breakaway force couplerincluding:

a. first and second members movable relative to each other, one membercoupled to the output of the transducer and the second member coupled tothe attachment point,

b. firstmeans for restraining the movement of the first and secondmembers relative to each other in a first direction below a firstbreakout value, and

c. second means for restraining the movement of the first and secondmembers relative to each other in a second direction below a secondbreakout value greater than the first breakout value, and

switching means carried by the coupler and actuated thereby when theforce applied thereto exceeds by a given amount the established breakoutvalues to disconnect the transducer from the generated control signal,

a position transducer in each of the control channels connected to therotary-to-linear motion transducer for generating a position feedbacksignal from the motion transducer to balance out the pilot generatedsignal connected thereto,

a torque tube having the common attachment points for the said first andsecond control pairs connected thereto and producing an output motionvarying in accordance with the pilot generated signal, and

means for converting the rotary motion at said torque tube into a linearmotion for controlling the power ram connected to an aircraft controlsurface.

12. A multiplex actuator for positioning an aircraft control surface asset forth in claim 11 wherein the rotary-to-linear motion transducer ineach control channel comprises a ballnut and lead-screw assembly whichmay be back driven by the other control channels coupled to said torquetube.

13. A multiplex actuator for positioning an aircraft control surface asset forth in claim 12 wherein the position transducer in each of thecontrol channels comprises a linear voltage differential transfonner.

14. A multiplex actuator for positioning an aircraft control surface asset forth in claim 11 including means for monitoring each of thebreakaway couplers for generating a pilot alarm signal when theswitching means of all but two of the four channels has been actuated byan excessive breakout force.

15. A multiplex actuator for positioning an aircraft control surface asset forth in claim 14 including a plurality of summing amplifiers eachhaving an output connected to one of the rotary-to-linear motiontransducers ofthe control channel through a switch actuated disconnectand a first input connected' to one of the pilot generated controlsignals and a second input connected to the respective feedback signalfrom the position transducer.

* at t a a

1. A multiplex actuator having an output motion that varies inaccordance with generated control signals, comprising: a plurality ofcontrol channels each including a rotary-tolinear motion transducerresponsive to a separate one of the generated control signals, motiontransmitting means for transferring the linear motion produced by thetransducer to an attachment point, said motion transmitting meanshaving: a. first and second members movable relative to each other, onemember coupled to the output of the transducer and the second membercoupled to the attachment point, b. first means for restraining themovement of the first and second members relative to each other in afirst direction below a first breakout value, and c. second means forrestraining the movement of the first and second members relative toeach other in a second direction below a second breakout value greaterthan the first breakout value, and switching means carried by saidmotion transmitting means and actuated thereby when the force appliedthereto exceeds the breakout values to disconnect the transducer fromthe generated control signal, and a forcing bar having the attachmentpoint of each of the plurality of control channels connected thereto andproducing an output motion varying in accordance with the generatedsignal energizing each of the control channels.
 2. A multiplex actuatorhaving an output motion that varies in accordance with generated controlsignals, comprising: a plurality of control channels each including arotary-to-linear motion transducer responsive to a separate one of thegenerated control signals, and motion transmitting means coupled to theoutput of the transducer for transferring the linear motion producedthereby to an attachment point, said motion transmitting meansincluding: a. first and second members movable relative to each other,one member coupled to the output of the transducer and the second membercoupled to the attachment point, b. first means for restraining themovement of the first and second members relative to each other in afirst direction below a first breakout value, and c. second means forrestraining the movement of the first and second members relative toeach other in a second direction below a second breakout value greaterthan the first breakout value, and a force bar having the attachmentpoint of each of the plurality of control channels connected thereto andproducing an output motion varying in accordance with the generatedsignals energizing each of the control channels.
 3. A multiplex actuatorhaving an output motion that varies in accordance with generated controlsignals as set forth in claim 2 including a position transducer in eachof the control channels coupled to said rotary-to-linear motiontransducer for generating a position feedback signal from the motiontransducer to balance out the generated control signal applied thereto.4. A multiplex actuator having an output motion that varies inaccordance with generated control signals as set forth in Claim 2wherein said force bar is a torque tube having a pivotal connection toeach of said plurality of control channels and producing a rotary outputfrom said actuator.
 5. A multiplex actuator having an output motion thatvaries in accordance with generated control signals, comprising: aplurality of control channels each including a rotary-to-linear motiontransducer responsive to a separate one of the generated controlsignals, and motion transmitting means coupled to the output of thetransducer for transferring the linear motion produced thereby to anattachment point, said motion transmitting means including: a. a housingpivotally connected to the attachment point, b. a connecting rodslidably positioned in said housing and coupled to the output of saidmotion transducer, c. a first collet fitted over said rod and engaging astop thereon and said housing, d. a second collet also fitted over saidrod and engaging a stop thereon, e. a first spring positioned betweensaid first and second collets in a preloaded condition, f. a thirdcollet concentrically mounted with said second collet and movable withrespect thereto and engaging said housing, and g. a second springpositioned between said first and third collets in a preloadedcondition, said first and second springs establishing an asymmetricalbreakout force for movement of the connecting rod with respect to thehousing, and a force bar having the attachment point of each of theplurality of control channels connected thereto and producing an outputmotion varying in accordance with the generated signals energizing eachof the control channels.
 6. A multiplex actuator for positioning anaircraft control surface in accordance with pilot generated controlsignals, comprising: a plurality of control channels each including arotary-to-linear motion transducer responsive to a separate one of thegenerated control signals, a breakaway force coupler coupled to theoutput of the transducer for transferring the output motion to anattachment point, said breakaway force coupler including: a. first andsecond members movable relative to each other, one member coupled to theoutput of the transducer and the second member coupled to the attachmentpoint, b. first means for restraining the movement of the first andsecond members relative to each other in a first direction below a firstbreakout value, and c. second means for restraining the movemenT of thefirst and second members relative to each other in a second directionbelow a second breakout value greater than the first breakout value, andswitching means carried by the breakaway coupler and actuated therebywhen the force applied thereto exceeds by a given amount the breakoutvalues to disconnect the transducer from the generated control signal, aposition transducer in each of the control channels coupled to saidrotary-to-linear motion transducer for generating a position feedbacksignal connected to the respective amplifier for that channel, and aforce bar having the attachment point of each of the plurality ofcontrol channels connected thereto and producing an output motion forcontrolling a power ram connected to said aircraft surface for varyingthe position of said surface in accordance with the pilot generatedcontrol signals.
 7. A multiplex actuator for positioning an aircraftcontrol surface as set forth in claim 6 including means for monitoringthe output of all of said plurality of control channels and generatingan alarm signal when the switching means carried by all but two of saidchannels is actuated.
 8. A multiplex actuator for positioning anaircraft control surface as set forth in claim 6 wherein said force baris a torque tube having a pivotal connection to each of said pluralityof control channels and producing a rotary output, and including arotary-to-linear motion transducer for generating the control signals tosaid power ram.
 9. A multiplex actuator for positioning an aircraftcontrol surface as set forth in claim 6 wherein said rotary-to-linearmotion transducer includes a lead screw connected to said breakawaycoupler and a ball-nut assembly as part of a motor armature, said leadscrew and ball-nut assembly may be back driven by a force applied to theoutput of said transducer.
 10. A multiplex actuator for positioning anaircraft control surface in accordance with pilot generated controlsignals, comprising: a plurality of control channels each including arotary-to-linear motion transducer responsive to a separate one of thegenerated control signals, a breakaway force coupler coupled to theoutput of the transducer for transferring the output motion to anattachment point, said breakaway force coupler including: a. a housingpivotally connected to the attachment point, b. a connecting rodslidably positioned in said housing and coupled to the output of saidmotion transducer, c. a first collet fitted over said rod and engaging astop thereon and said housing, d. a second collet also fitted over saidrod and engaging a stop thereon, e. a first spring positioned betweensaid first and second collets in a preloaded condition, f. a thirdcollet concentrically mounted with said second collet and movable withrespect thereto and engaging said housing, and g. a second springpositioned between said first and third collets in a preloadedcondition, said first and second springs establishing an asymmetricalbreakout force for movement of the connecting rod with respect to thehousing, and switching means carried by the breakaway coupler andactuated thereby when the force applied thereto exceeds by a givenamount the breakout values to disconnect the transducer from thegenerated signal, a position transducer in each of the control channelscoupled to said rotary-to-linear motion transducer for generating aposition feedback signal connected to the respective amplifier for thatchannel, and a force bar having the attachment point of each of theplurality of control channels connected thereto and producing an outputmotion for controlling a power ram connected to said aircraft surfacefor varying the position of said surface in accordance with the pilotgenerated control signals.
 11. A multiplex actuator for positioning anaircraft control surface by means of a power ram in accordance withpilot generated control signals, comprising: a first control channelpair coupled together in a force summing arrangement to a commonattachment point, each of said control channels including arotary-to-linear motion transducer responsive to a separate one of thegenerated control signals, a breakaway force coupler engaging the outputof the transducer for transferring the linear motion output thereof tothe common attachment point, said breakaway force coupler including: a.first and second members movable relative to each other, one membercoupled to the output of the transducer and the second member coupled tothe attachment point, b. first means for restraining the movement of thefirst and second members relative to each other in a first directionbelow a first breakout value, and c. second means for restraining themovement of the first and second members relative to each other in asecond direction below a second breakout value greater than the firstbreakout value, and switching means carried by the coupler and actuatedthereby when the force applied thereto exceeds by a given amount theestablished breakout values to disconnect the transducer from thegenerated control signal, a second control channel pair coupled togetherin a force summing arrangement to a common attachment point, each of thecontrol channels including a rotary-to-linear motion transducerresponsive to a separate one of the generated control signals, abreakaway force coupler engaging the output of the transducer fortransferring the linear motion output thereof to the common attachmentpoint, said breakaway force coupler including: a. first and secondmembers movable relative to each other, one member coupled to the outputof the transducer and the second member coupled to the attachment point,b. first means for restraining the movement of the first and secondmembers relative to each other in a first direction below a firstbreakout value, and c. second means for restraining the movement of thefirst and second members relative to each other in a second directionbelow a second breakout value greater than the first breakout value, andswitching means carried by the coupler and actuated thereby when theforce applied thereto exceeds by a given amount the established breakoutvalues to disconnect the transducer from the generated control signal, aposition transducer in each of the control channels connected to therotary-to-linear motion transducer for generating a position feedbacksignal from the motion transducer to balance out the pilot generatedsignal connected thereto, a torque tube having the common attachmentpoints for the said first and second control pairs connected thereto andproducing an output motion varying in accordance with the pilotgenerated signal, and means for converting the rotary motion at saidtorque tube into a linear motion for controlling the power ram connectedto an aircraft control surface.
 12. A multiplex actuator for positioningan aircraft control surface as set forth in claim 11 wherein therotary-to-linear motion transducer in each control channel comprises aball-nut and lead-screw assembly which may be back driven by the othercontrol channels coupled to said torque tube.
 13. A multiplex actuatorfor positioning an aircraft control surface as set forth in claim 12wherein the position transducer in each of the control channelscomprises a linear voltage differential transformer.
 14. A multiplexactuator for positioning an aircraft control surface as set forth inclaim 11 including means for monitoring each of the breakaway couplersfor generating a pilot alarm signal when the switching means of all buttwo of the four channels has been actuated by an excessive breakoutforce.
 15. A multiplex actuator for positioning an aircraft controlsurface as set forth in claim 14 including a plurality of summingamplifiers each having an output connected to one of therotary-to-linear motion transducers of the control channel through aswitch actuaTed disconnect and a first input connected to one of thepilot generated control signals and a second input connected to therespective feedback signal from the position transducer.